As a torsional vibration attenuation apparatus of this type, there has so far been known a torsional vibration attenuation apparatus which comprises a drive source such as an internal combustion engine, an electric motor and the like, and driven wheels drivably connected with the drive source to be driven by the rotational torque transmitted from the drive source. The conventional torsional vibration attenuation apparatus is adapted to absorb the torsional vibrations between the drive source and a drive system having transmission gear sets.
The known torsional vibration attenuation apparatus is constituted for example by a driving rotation member adapted to be selectively coupled with or released from a drive source side flywheel, a driven rotational member connected with an input shaft forming part of a transmission, and a resilient member having the driving rotation member and the driven rotation member circumferentially resiliently connected with each other (see for example Patent Document 1).
The driving rotation member is constituted by a clutch disc, and a pair of disc plates provided radially inwardly of the clutch disc, while the driven rotation member is partly constituted by a hub not rotatably and axially movably connected with the input shaft of the transmission and disposed between the disc plates.
The hub has a cylindrical boss splined to the input shaft and a disc-like flange radially outwardly extending. The resilient member is merely constituted by a coil spring accommodated in a window hole formed in the flange and having circumferential both end portions supported on the circumferential both ends of the window hole and the circumferential both ends of additional window holes respectively formed in the pair of disc plates.
The known torsional vibration attenuation apparatus previously mentioned is constructed to have the coil spring circumferentially compressed between the clutch disc and the pair of disc plates and the hub when the clutch disc and the pair of disc plates and the hub are relatively rotated with one another, thereby making it possible to absorb and attenuate the torsional vibrations inputted to the driven rotation member from the driving rotation member.
On the other hand, it is well known in the art that there are generated abnormal noises at the idling time of a vehicle, and abnormal noises and muffled noises at the travelling time of the vehicle as transmission side noises generated by the torsional vibrations. It is therefore required to suitably set the torsional property of the torsional vibration attenuation apparatus in order to absorb the torsional vibrations leading to the generation of the above abnormal noises.
Here, the abnormal noises generated at the idling time of the vehicle are known to be constituted by what is called clattering noises, one kind of abnormal noises emitted as being “clattering” caused by the collisions of the gear pairs with no load. Those noises are generally caused by torsional vibrations originated from the rotational fluctuation caused by the torque fluctuation of the driving source at the idling time of the vehicle immediately after being speed changed to the neutral.
Further, the abnormal noises generated at the travelling time of the vehicle are known to be constituted partly by what is called chinking noises, one kind of abnormal noises emitted as being “chinking” from the collisions of the slipping gear pairs of the transmission gear sets caused by the torsional vibrations originated from the rotational fluctuation in response to the torque fluctuation of the driving source and caused by the torsional resonance of the driving system during the acceleration and deceleration of the vehicle.
In addition, the muffled noises are known as one kind of abnormal noises to be generated in the passenger room by the vibrations caused by the torsional resonance of the driving system originated from the torque fluctuation of the driving system. The torsional resonance of the driving system is usually caused at the normal travelling operation (for example around 2500 rpm of the rotational speed of the internal combustion engine), so that there is caused muffled noises in the passenger room at the normal travelling operation.
One of the conventional torsional vibration attenuation apparatuses having a torsional property suitably set is known for example by the following Patent Document 2. The known torsional vibration attenuation apparatus comprises a cylindrical boss constituting a driven rotation member, and a disc-like flange radially outwardly extending from the boss. Between the outer peripheral portion of the boss and the inner peripheral portion of the flange is disposed a small coil spring having a small spring constant to absorb the torsional vibrations of the boss and the flange.
A pair of disc plates are each formed with a first window portion and a second window portion which are spaced apart from each other in the circumferential direction of the disc plates.
The flange is formed with a first window hole and a second window hole respectively facing the first window portion and the second window portion. The first window portion and the first window hole accommodate therein a first coil spring and a first seat member. The first coil spring has a spring constant larger than the small spring.
The second window portion and the second window hole accommodate therein a second coil spring and a second seat member. The second coil spring has a spring constant larger than the small spring.
The first seat member is circumferentially spaced apart from the first window hole. The first coil spring has such a torsional property that the first coil spring is not compressed in a small torsional angle area where the second spring is compressed but compressed in a large torsional angle area.
The driving rotation member and the driven rotation member in the torsional vibration attenuation apparatus have a torsional property as shown in FIG. 17.
More specifically, only the small coil spring is compressed in the small torsional area of the clutch disc and the boss as in the state of the vehicle changed in speed from the idling state to the neutral state, thereby making the rigidity low in the small torsional angle area to suppress the clattering noises from being generated.
Further in the large torsional angle area, only the second coil spring is compressed, thereby obtaining an intermediate rigidity torsional property having a torque gently raised as shown by an arrow “a” in FIG. 17, thereby making it possible to suppress the muffled noises from being generated.
When the torsional angle is further increased to take a predetermined level, the first coil spring and the second coil spring are concurrently compressed to obtain a high rigidity torsional property having the torque sharply raised as shown by an arrow “b” in FIG. 17, thereby making it possible to suppress the chinking noises from being generated. This means that a multi-staged torsional property can be obtained.
However, the conventional torsional vibration attenuation apparatus encounter such a problem that there is caused rattling noises of the gears acting to transmit the rotational torque in the transmission at the stepped portion (bent portion in the graph) where the raising ratio of the transmission torque is fluctuated.
The rattling noises are constituted by a low frequency wave, and thus called “rattling noises”. When the torque to be transmitted to the driven rotation member from the driving rotation member for example in the travelling state during the slow deceleration time of the vehicle is approximately zero Nm, the conventional torsional vibration attenuation apparatus encounters such a problem that there is generated an abrupt torque fluctuation in the stepped portion of the torsional property, thereby causing abnormal noises such as gear clattering noises caused by the bouncing of the gears.
In view of this problem, another torsional vibration attenuation apparatus capable of suppressing the rattling noses is known for example by the Patent Document 3. The known torsional vibration attenuation apparatus is not constructed to have a multi-staged torsional property but in the non-linear shape to make the torsional property not formed with the stepped portion of the torque fluctuation.
The known torsional vibration attenuation apparatus disclosed in the Patent Document 3 comprises a driving rotation member integrally rotated with the internal combustion engine, a driven rotation member coaxially and relatively rotatably disposed with the driving rotation member, and a displacement member relatively displaced with the driven rotation member. The displacement member is formed in the driving rotation member and has a contact portion moving along the contacted surface constituted to have the curvature varied in response to the relative rotation angle of the driving rotation member and the driven rotation member. The relative displacement of the displacement member is performed by the contact portion moving along the contacted surface in response to the relative rotation of the driving rotation member and the driven rotation member. The known torsional vibration attenuation apparatus further comprises a resilient member resiliently contractible in response to the relative displacement of the displacement member, and stopper portions respectively provided on the driving rotation member and the displacement member to be engageable with each other to regulate the relative rotation of the displacement member and the driving rotation member, thereby regulating the relative rotation of the driving rotation member and the driven rotation member.